10-04-2013, 03:20 PM
3 TO 8 DECODER (IC 74138)
ABSTRACT:
To study and simulate IC 74138 using VHDL.
THEORY:
The74138 is a commercially available MSI 3 to 8 decoder. The 74138 has3 enable inputs (G1, G2A_L, G2B_L), all of which must be asserted for the selected output it has 3 active inputs and 8 active low outputs. Based on the select inputs (n) one output among 2n outputs.
PROCEDURE:
The IC 74138 Design is entered through VHDL.
Simulate the design by applying test vectors-G1, G2A_L, G2B_L ,I and observing output z.
It is required to lock the pins and give timing constraints.
Implement the design by passing the design by various stages by mapping, time analysis and bit stream. For locking the pins write UCF file before implementation and guide the same through option set control files. Output of the implementation is .JED file, which can be directly programmed into target device FPGA.
The last step is programming in which the programme can physically download the architecture from computer to target device FPGA